New synthesis method of HA/P(D,L)LA composites: study of fibronectin adsorption and their effects in osteoblastic behavior for bone tissue engineering

ABSTRACT

A novel synthetic method to synthesize hydroxyapatite​/poly (D,​L) lactic acid biocomposite is presented in this study by mixing only the precursors hydroxyapatite and (D,​L) LA monomer without adding neither solvent nor catalyst.  Three compns. were successfully synthesized with the wt. ratios of 1​/1, 1​/3, and 3​/5 (hydroxyapatite​/(D,​L) lactic acid)​, and the grafting efficiency of poly (D,​L) lactic acid on hydroxyapatite surface reaches up to 84 %.  SEM and Fourier transform IR spectroscopy showed that the hydroxyapatite particles were successfully incorporated into the poly (D,​L) lactic acid polymer and X ray diffraction anal. showed that hydroxyapatite preserved its crystallinity after poly (D,​L) lactic acid grafting.  Differential scanning calorimetry shows that Tg of hydroxyapatite​/poly (D,​L) lactic acid composite is less than Tg of pure poly (D,​L) lactic acid, which facilitates the shaping of the composite obtained.  The addn. of poly (D,​L) lactic acid improves the adsorption properties of hydroxyapatite for fibronectin extracellular matrix protein.  Furthermore, the presence of poly (D,​L) lactic acid on hydroxyapatite surface coated with fibronectin enhanced pre-​osteoblast STRO-​1 adhesion and cell spreading.  These results show the promising potential of hydroxyapatite​/poly (D,​L) lactic acid composite as a bone substitute material for orthopedic applications and bone tissue engineering.